Mechanistic interpretation of the redox behaviour of diphenylamine

The oxidative mechanism of diphenylamine does not seem to involve the formation of diphenylbenzidine or diphenylbenzidine green (DBG) as intermediates, but these are observed in the reduction of diphenylbenzidine violet. The diphenylbenzidine green is generally obtained as an insoluble solid. It is a free radical. It is concluded that for kinetic reasons the different oxidation products of diphenylamine may not necessarily appear together nor in fixed generic sequence in an oxidation or reduction reaction but may be obtained individually under appropriate experimental conditions. The decay of diphenylbenzidine violet seems to involve a disproportionation reaction to give DBG, rather than a polymerization reaction.